if you use offzip on it it appears they used zlib chunks the start offset if the offset directly after the word zlib.
then it reads zlib chunks till the end of the file.
i am not sure how to read the starting header of the file before the zlib section.

Have you tried it? It should work on any zlib compressed psarc files from UDF. For files that aren't zlib, if someone could post a small chunk of the file, I'll try to update the extractor for that type of compression.